It's amazing just how useful many of the hidden accessibility features built into the iPhone are. I've already talked about how amazingly useful the hidden shortcut menu is, but here's another one I've been using lately -- the Magnifier app.

The Magnifier app works a bit like the Camera app, but gives you greater power to zoom in on the image (beyond the point where you'd be able to take a decent photo) as well as access to other features such as locking the exposure and adjusting the brightness and contrast of the image.

You can enable the magnifier feature as follows:

Settings > General > Accessibility > Magnifier and from there toggle on Magnifier

Now when you want to bring up the Magnifier app simply triple-click on the Home button.